Telephone system



May 20, 1924. v 1,494,878

W. F. ANDRICK- TELEPHONE SYSTEM Filed March 18. 1922 Patented May 20, 1924.

UNITED STATES PATENT o F1cE.

WALLACE 1?. ANDRICK, OF HOHO'KUS, NEW JERSEY, ASSIGNOR IO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N; Y., A'CORPOBATION' OF YORK.

TELEPHONE SYSTEM.

tem and particularly to a circuit arrange-.

ment for. such a system wherein one of a plurality of telephone substations may be. connected to a common line to the exclusion, An instance of this kind occurs in systems in which a particular sub- 7 of other stations.

station of a group is given soleuse of a trunk llne leading to a central oflice durlng connection therewith so as to insure secrecy of conversation.

In some systems of this nature, a key 15 employed at theparticular or preferred sub a station which, when actuated,

I excludes all other substations from the trunk ,line.

-It has been found that if the key is aceiden 4 trunk.

' It is therefore an object of this invention to prevent a main station in a system of this kind from disconnecting other stations from, a line except when the main station is tele' phonically connected to the line.

A feature of the invention consists in the. provislon of a circuit arrangement such that the depression of the key at the main or preferred substation effects the disconnec tion of the remaining stations associated with the trunk line only when the receiver at the preferred substation is removed from the switch hook.

, In the accompanying drawing, the invention is illustrated diagrammatically in its application to an intercommunicating syssubstations Q "and D. of the system have.

tem, only such portions being shown as are necessary to its understanding.

A plurality of intercommunicating sub stations A, C and D, of which only one is illustratedin detail at A,are joined by a trunk line to a battery B. at a central sta The energized. I If the subscriber at station A wishes to Application filed March 18, 1922. Serial 110 544,733.

communication with the trunk by way of the leads L through theback contacts 10 of a relay15. The winding. of relay 15 receives converse vwitha partyat the main exchange without permitting access of the other stations. to the line L, heiwill' remove the receiver from the switch hook and, ifno conversation visheard on the line, operate the key It will. be understood that insome systems tov which th-is invention is applicable,

the trunk 3 line L will .be connected to a line relay (not shown). at'the centraloflic'e having batteryand ground connected thereto in a manner well known in the art.- .The removalofthe receiver :from the switch hook AQwill causea line lamp (not shown) to vlight at the centraloffice, the well-known '[manner and the operator 'may insert, the

answering end of a cord circuit, into the jack (not shown of the line thereby cone necting the, battery B in circuit with, the

station A. The removal of the receiver from the switch 'hookat stationA causes current fromthe battery B at the central office to How over the trunk line L throughthe station A thereby causing the energization of relay 12. Relay 12 in operating closes its contacts thereby preparing a circuit for the actuation of relay 15. The actuation of key K then causesthe energization of relay 15 over a path extending from the plus pole of battery B through the winding of relay 15,

contacts of relay 12, contacts of key K to the minus poleof the battery B. Relay 15 in operating opens its contacts 10, 10 thereby disconnecting the stations C and D from the trunk leads L, L and closes its contacts 14, 14: thereby connecting a buzzer 11 in circuit with the stations C and D Relay 15 in operating also completes a locking circuit for'itselfindepend'ent of the key K over a.

path extending from the plus pole, of battery B, throughfthe winding of relay 15, contacts of relay 12, 'upper contacts'of relay 15 t9 t ine P l 9? battery B p p buzzer 11.

At the termination of the conversation,

the return of the receiver to its switch hook at station A causes the release of rela 12 and relay 12 in releasing opens the loc ing circuit for relay 1 5,which in releasing restores the circuit to normalf The system is then in condition for a callfrom any of the substations.

It will be obvious from the preceding description that if the preferred station is connected to the trunk on either incoming or outgoing connections, all other stations may be barred from the trunk by momentarily depressing the non-locking key. It will also be noted that an accidental or other actuation of the key K, when the receiver of the station A is not removed from the switch hook, will not cause disconnection of stations, such as C and D, from the trunk line L since the circuit for relay 15 can only be completed when relay 12 is energized and its contacts are closed. I,

What is claimed is: I

l. The combination with a plurality of telephone substations and a line therefor, of a relay for governing the connection of certain of the substations to the line, a relay included in the line energized by one of said substations, and means situated at the said one substation for controlling said relay only when said line relay is energized.

2. A plurality of associated telephone stations, a line for connecting said stationsto another station and a plurality of electron e chanisms individual to one of the associated stations and being adapted to vary the connection of such stations to the line, one

of the electromechanisms being energized over the line and the other locally, said other mechanism being capable of being operated only when said firstmentioned electromechanism is energized. V v i i 3. In a telephone system, the combination with a plurality of substations, of a line for connecting said substations to another station, a plurality of electromechanisms for disconnecting from the line all but a particular substation, and aswitchhook at said particular substation for controlling the initial energization of one of the electromechanisnis by eurrent locally, another ofthe electromecl ianisms continuing such energization and being energized only when said particular substation i's'in use. 1 I i 4. In a telephone system, the combination with a plurality of substations, of a line normally connected to one of said substations for connecting one of said substations to another station, a plurality of electromechanisms for varying the connection of the substations to the line, means at the substation for controlling the action of said 'electromechanisms only when the. receiver one substation for controlling theaction of said electromechanisms only when the receiver of the substation is'ofi the switchhook, and a switchhook at the said one substation for controlling the restoration of said electromechanisms to normal.

6. In a telephone system, the combination with a plurality of substations, of a line normally connected to one of said substa tions for connecting said substations to another station, a plurality of electromechanisms for varying the connection of the substations to the line, and a manually operable switch ata substation for controlling the action of one of said electromechanisms only when the receiver of the substation is off the hook, the restoration of said electromechanisms being controlled by the substation switch hook. v

7. A trunk line, a preferred substation directly connected thereto, other, substations, a disconnecting relay through'the back contacts of which said-other substations are joined to the trunk, a relay having its winding included in the trunk, and a circuit including a key at the preferred substation and a contact of said trunk relay for energizing the disconnecting relay.

8. A trunk line, a preferred substation directly connected thereto, other substations, a disconnecting relay through the back contacts of which said other substations -,are joined to the trunk, a relay having its winding'included in the trunk, a circuit including a key at the preferred substation and a contact of said trunk relay for energizing the disconnectingrelay, and a l ki i suit for the disconnecting relay including the contacts of the trunk relay.

9. The combination of a plurality of telephone substations and a line therefor, of a first and asecondrelay governing the connections ofthe substations to the line, means including a switchhook for energizing the first relay, means including a key for ener including a contact of said key and said device to prevent the association of said telephone station With said trunk line.

In Witness whereof, I hereunto subscribe my name this 14th day of March, A. D.

WALLACE P. ANDRIGK. 

